The present disclosure relates to a fine particle measurement device. More specifically, the present disclosure relates to a fine particle measurement device which is capable of forming a beam spot of a sufficient size to irradiate fine particles with a laser at a uniform intensity.
Fine particle measurement devices that measure the characteristics of fine particles such as cells optically are known (for example, flow cytometers).
In flow cytometers, a sample liquid that includes cells is sent through a flow channel that is formed in flow cells or microchips, cells that flow inside of the flow channel are irradiated with a laser and the optical characteristics of the cells are measured by detecting the fluorescent light or scattered light that is generated from the cells using a detector. In addition, in flow cytometers, separation and collection of determined populations (groups) from the cells is performed when the results of measurement of optical characteristics and predetermined conditions are satisfied.
For example, in Japanese Unexamined Patent Application Publication No. 2010-190680, “a fine particle fractional collection device including a microchip in which a flow channel through which a liquid containing fine particles flows, and an orifice that expels the liquid that flows in the flow channel to the space outside the chip are disposed, a vibration element for discharging liquid by forming droplets in the orifice, charging means for applying a charge to discharged droplets, optical detecting means for detecting the optical characteristics of the fine particles that flow through the flow channel, paired electrodes arranged along the direction of movement of a droplet discharged to the space outside the chip and opposed with the moving droplet therebetween, and two or more vessels for collecting the droplets that pass between the paired electrodes” is disclosed as a microchip flow cytometer.
In flow cytometers, since cells that flow through a flow channel are irradiated by a laser at a uniform intensity, the beam spot of the laser that is concentrated on the flow channel is formed in a manner such that the spot diameter becomes a sufficient size with respect to the width of the flow channel. By forming the beam spot to be sufficiently large with respect to the width of the flow channel, it is possible to irradiate all of the cells with a laser at a uniform intensity since the beam spot is passed without being dependent on the flow position of each cell in the flow channel.
In Japanese Unexamined Patent Application Publication No. 2012-26754, a fine particle measurement device including a light irradiation system that transmits light from a light source through a phase level difference element that is divided into a plurality of regions and concentrates light on a sample flow in which fine particles flow is disclosed. In this fine particle measurement device, by generating phase differences between the wave surfaces of the light that is transmitted through each region of the phase level difference element, a beam spot that has a uniform distribution of intensity over a wide range is formed and the effective intensity of the laser with which the fine particles in the sample flow are irradiated is homogenized.